jdsample.c

00001 /*
00002  * jdsample.c
00003  *
00004  * Copyright (C) 1991-1996, Thomas G. Lane.
00005  * Modified 2002-2015 by Guido Vollbeding.
00006  * This file is part of the Independent JPEG Group's software.
00007  * For conditions of distribution and use, see the accompanying README file.
00008  *
00009  * This file contains upsampling routines.
00010  *
00011  * Upsampling input data is counted in "row groups".  A row group
00012  * is defined to be (v_samp_factor * DCT_v_scaled_size / min_DCT_v_scaled_size)
00013  * sample rows of each component.  Upsampling will normally produce
00014  * max_v_samp_factor pixel rows from each row group (but this could vary
00015  * if the upsampler is applying a scale factor of its own).
00016  *
00017  * An excellent reference for image resampling is
00018  *   Digital Image Warping, George Wolberg, 1990.
00019  *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
00020  */
00021 
00022 #define JPEG_INTERNALS
00023 #include "jinclude.h"
00024 #include "jpeglib.h"
00025 
00026 
00027 /* Pointer to routine to upsample a single component */
00028 typedef JMETHOD(void, upsample1_ptr,
00029         (j_decompress_ptr cinfo, jpeg_component_info * compptr,
00030          JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));
00031 
00032 /* Private subobject */
00033 
00034 typedef struct {
00035   struct jpeg_upsampler pub;    /* public fields */
00036 
00037   /* Color conversion buffer.  When using separate upsampling and color
00038    * conversion steps, this buffer holds one upsampled row group until it
00039    * has been color converted and output.
00040    * Note: we do not allocate any storage for component(s) which are full-size,
00041    * ie do not need rescaling.  The corresponding entry of color_buf[] is
00042    * simply set to point to the input data array, thereby avoiding copying.
00043    */
00044   JSAMPARRAY color_buf[MAX_COMPONENTS];
00045 
00046   /* Per-component upsampling method pointers */
00047   upsample1_ptr methods[MAX_COMPONENTS];
00048 
00049   int next_row_out;     /* counts rows emitted from color_buf */
00050   JDIMENSION rows_to_go;    /* counts rows remaining in image */
00051 
00052   /* Height of an input row group for each component. */
00053   int rowgroup_height[MAX_COMPONENTS];
00054 
00055   /* These arrays save pixel expansion factors so that int_expand need not
00056    * recompute them each time.  They are unused for other upsampling methods.
00057    */
00058   UINT8 h_expand[MAX_COMPONENTS];
00059   UINT8 v_expand[MAX_COMPONENTS];
00060 } my_upsampler;
00061 
00062 typedef my_upsampler * my_upsample_ptr;
00063 
00064 
00065 /*
00066  * Initialize for an upsampling pass.
00067  */
00068 
00069 METHODDEF(void)
00070 start_pass_upsample (j_decompress_ptr cinfo)
00071 {
00072   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00073 
00074   /* Mark the conversion buffer empty */
00075   upsample->next_row_out = cinfo->max_v_samp_factor;
00076   /* Initialize total-height counter for detecting bottom of image */
00077   upsample->rows_to_go = cinfo->output_height;
00078 }
00079 
00080 
00081 /*
00082  * Control routine to do upsampling (and color conversion).
00083  *
00084  * In this version we upsample each component independently.
00085  * We upsample one row group into the conversion buffer, then apply
00086  * color conversion a row at a time.
00087  */
00088 
00089 METHODDEF(void)
00090 sep_upsample (j_decompress_ptr cinfo,
00091           JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
00092           JDIMENSION in_row_groups_avail,
00093           JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
00094           JDIMENSION out_rows_avail)
00095 {
00096   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00097   int ci;
00098   jpeg_component_info * compptr;
00099   JDIMENSION num_rows;
00100 
00101   /* Fill the conversion buffer, if it's empty */
00102   if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
00103     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
00104      ci++, compptr++) {
00105       /* Invoke per-component upsample method.  Notice we pass a POINTER
00106        * to color_buf[ci], so that fullsize_upsample can change it.
00107        */
00108       (*upsample->methods[ci]) (cinfo, compptr,
00109     input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
00110     upsample->color_buf + ci);
00111     }
00112     upsample->next_row_out = 0;
00113   }
00114 
00115   /* Color-convert and emit rows */
00116 
00117   /* How many we have in the buffer: */
00118   num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
00119   /* Not more than the distance to the end of the image.  Need this test
00120    * in case the image height is not a multiple of max_v_samp_factor:
00121    */
00122   if (num_rows > upsample->rows_to_go) 
00123     num_rows = upsample->rows_to_go;
00124   /* And not more than what the client can accept: */
00125   out_rows_avail -= *out_row_ctr;
00126   if (num_rows > out_rows_avail)
00127     num_rows = out_rows_avail;
00128 
00129   (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
00130                      (JDIMENSION) upsample->next_row_out,
00131                      output_buf + *out_row_ctr,
00132                      (int) num_rows);
00133 
00134   /* Adjust counts */
00135   *out_row_ctr += num_rows;
00136   upsample->rows_to_go -= num_rows;
00137   upsample->next_row_out += num_rows;
00138   /* When the buffer is emptied, declare this input row group consumed */
00139   if (upsample->next_row_out >= cinfo->max_v_samp_factor)
00140     (*in_row_group_ctr)++;
00141 }
00142 
00143 
00144 /*
00145  * These are the routines invoked by sep_upsample to upsample pixel values
00146  * of a single component.  One row group is processed per call.
00147  */
00148 
00149 
00150 /*
00151  * For full-size components, we just make color_buf[ci] point at the
00152  * input buffer, and thus avoid copying any data.  Note that this is
00153  * safe only because sep_upsample doesn't declare the input row group
00154  * "consumed" until we are done color converting and emitting it.
00155  */
00156 
00157 METHODDEF(void)
00158 fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
00159            JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
00160 {
00161   *output_data_ptr = input_data;
00162 }
00163 
00164 
00165 /*
00166  * This is a no-op version used for "uninteresting" components.
00167  * These components will not be referenced by color conversion.
00168  */
00169 
00170 METHODDEF(void)
00171 noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
00172            JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
00173 {
00174   *output_data_ptr = NULL;  /* safety check */
00175 }
00176 
00177 
00178 /*
00179  * This version handles any integral sampling ratios.
00180  * This is not used for typical JPEG files, so it need not be fast.
00181  * Nor, for that matter, is it particularly accurate: the algorithm is
00182  * simple replication of the input pixel onto the corresponding output
00183  * pixels.  The hi-falutin sampling literature refers to this as a
00184  * "box filter".  A box filter tends to introduce visible artifacts,
00185  * so if you are actually going to use 3:1 or 4:1 sampling ratios
00186  * you would be well advised to improve this code.
00187  */
00188 
00189 METHODDEF(void)
00190 int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
00191           JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
00192 {
00193   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00194   JSAMPARRAY output_data = *output_data_ptr;
00195   register JSAMPROW inptr, outptr;
00196   register JSAMPLE invalue;
00197   register int h;
00198   JSAMPROW outend;
00199   int h_expand, v_expand;
00200   int inrow, outrow;
00201 
00202   h_expand = upsample->h_expand[compptr->component_index];
00203   v_expand = upsample->v_expand[compptr->component_index];
00204 
00205   inrow = outrow = 0;
00206   while (outrow < cinfo->max_v_samp_factor) {
00207     /* Generate one output row with proper horizontal expansion */
00208     inptr = input_data[inrow];
00209     outptr = output_data[outrow];
00210     outend = outptr + cinfo->output_width;
00211     while (outptr < outend) {
00212       invalue = *inptr++;   /* don't need GETJSAMPLE() here */
00213       for (h = h_expand; h > 0; h--) {
00214     *outptr++ = invalue;
00215       }
00216     }
00217     /* Generate any additional output rows by duplicating the first one */
00218     if (v_expand > 1) {
00219       jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
00220             v_expand-1, cinfo->output_width);
00221     }
00222     inrow++;
00223     outrow += v_expand;
00224   }
00225 }
00226 
00227 
00228 /*
00229  * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
00230  * It's still a box filter.
00231  */
00232 
00233 METHODDEF(void)
00234 h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
00235            JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
00236 {
00237   JSAMPARRAY output_data = *output_data_ptr;
00238   register JSAMPROW inptr, outptr;
00239   register JSAMPLE invalue;
00240   JSAMPROW outend;
00241   int outrow;
00242 
00243   for (outrow = 0; outrow < cinfo->max_v_samp_factor; outrow++) {
00244     inptr = input_data[outrow];
00245     outptr = output_data[outrow];
00246     outend = outptr + cinfo->output_width;
00247     while (outptr < outend) {
00248       invalue = *inptr++;   /* don't need GETJSAMPLE() here */
00249       *outptr++ = invalue;
00250       *outptr++ = invalue;
00251     }
00252   }
00253 }
00254 
00255 
00256 /*
00257  * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
00258  * It's still a box filter.
00259  */
00260 
00261 METHODDEF(void)
00262 h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
00263            JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
00264 {
00265   JSAMPARRAY output_data = *output_data_ptr;
00266   register JSAMPROW inptr, outptr;
00267   register JSAMPLE invalue;
00268   JSAMPROW outend;
00269   int inrow, outrow;
00270 
00271   inrow = outrow = 0;
00272   while (outrow < cinfo->max_v_samp_factor) {
00273     inptr = input_data[inrow];
00274     outptr = output_data[outrow];
00275     outend = outptr + cinfo->output_width;
00276     while (outptr < outend) {
00277       invalue = *inptr++;   /* don't need GETJSAMPLE() here */
00278       *outptr++ = invalue;
00279       *outptr++ = invalue;
00280     }
00281     jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
00282               1, cinfo->output_width);
00283     inrow++;
00284     outrow += 2;
00285   }
00286 }
00287 
00288 
00289 /*
00290  * Module initialization routine for upsampling.
00291  */
00292 
00293 GLOBAL(void)
00294 jinit_upsampler (j_decompress_ptr cinfo)
00295 {
00296   my_upsample_ptr upsample;
00297   int ci;
00298   jpeg_component_info * compptr;
00299   int h_in_group, v_in_group, h_out_group, v_out_group;
00300 
00301   upsample = (my_upsample_ptr)
00302     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00303                 SIZEOF(my_upsampler));
00304   cinfo->upsample = &upsample->pub;
00305   upsample->pub.start_pass = start_pass_upsample;
00306   upsample->pub.upsample = sep_upsample;
00307   upsample->pub.need_context_rows = FALSE; /* until we find out differently */
00308 
00309   if (cinfo->CCIR601_sampling)  /* this isn't supported */
00310     ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
00311 
00312   /* Verify we can handle the sampling factors, select per-component methods,
00313    * and create storage as needed.
00314    */
00315   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
00316        ci++, compptr++) {
00317     /* Compute size of an "input group" after IDCT scaling.  This many samples
00318      * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
00319      */
00320     h_in_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) /
00321          cinfo->min_DCT_h_scaled_size;
00322     v_in_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
00323          cinfo->min_DCT_v_scaled_size;
00324     h_out_group = cinfo->max_h_samp_factor;
00325     v_out_group = cinfo->max_v_samp_factor;
00326     upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
00327     if (! compptr->component_needed) {
00328       /* Don't bother to upsample an uninteresting component. */
00329       upsample->methods[ci] = noop_upsample;
00330       continue;     /* don't need to allocate buffer */
00331     }
00332     if (h_in_group == h_out_group && v_in_group == v_out_group) {
00333       /* Fullsize components can be processed without any work. */
00334       upsample->methods[ci] = fullsize_upsample;
00335       continue;     /* don't need to allocate buffer */
00336     }
00337     if (h_in_group * 2 == h_out_group && v_in_group == v_out_group) {
00338       /* Special case for 2h1v upsampling */
00339       upsample->methods[ci] = h2v1_upsample;
00340     } else if (h_in_group * 2 == h_out_group &&
00341            v_in_group * 2 == v_out_group) {
00342       /* Special case for 2h2v upsampling */
00343       upsample->methods[ci] = h2v2_upsample;
00344     } else if ((h_out_group % h_in_group) == 0 &&
00345            (v_out_group % v_in_group) == 0) {
00346       /* Generic integral-factors upsampling method */
00347       upsample->methods[ci] = int_upsample;
00348       upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
00349       upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
00350     } else
00351       ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
00352     upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
00353       ((j_common_ptr) cinfo, JPOOL_IMAGE,
00354        (JDIMENSION) jround_up((long) cinfo->output_width,
00355                   (long) cinfo->max_h_samp_factor),
00356        (JDIMENSION) cinfo->max_v_samp_factor);
00357   }
00358 }